Comment 2 for bug 1450912

This isn't 1.16 behavior. This is "Client.ServiceDeploy" will go to the charm store directly. It is true that the juju CLI only did this in 1.16 and started going to the charm store directly from 1.18 onwards. However, I believe Juju-GUI and obviously Juju Quickstart both rely on this behavior.

If we want to remove this functionality, we definitely need to preserve it in the v0 of Client API, and we can create a v1 of the Client API that no longer supports this functionality. The code comment in question is semi-bogus as "juju" is not the only client of our API.